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89038cc87d
linux/kernel
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Thomas Gleixner 89038cc87d locking/rt: Fix the incorrect RCU protection in rt_spin_unlock() 
rt_spin_unlock() releases the RCU protection before unlocking the
lock. That opens the door for the following UAF scenario:

 T1					T2
 spin_lock(&p->lock);		rcu_read_lock();
 invalidate(p);			p = rcu_dereference(ptr);
 rcu_assign_pointer(ptr, NULL);	if (!p) return;
 spin_unlock(&p->lock);		spin_lock(&p->lock)
 				   lock(&lock->lock);
				   rcu_read_lock();
 kfree_rcu(p);			rcu_read_unlock();
				....
				spin_unlock(&p->lock)
				  rcu_read_unlock(); // Ends grace period
 rcu_do_batch()
   kfree(p);
			    UAF ->	  rt_mutex_cmpxchg_release(&lock->lock...)

Regular spinlocks keep preemption disabled accross the unlock operation,
which provides full RCU protection, but the RT substitution fails to
resemble that. Same applies for the rwlock substitution.

Move the rcu_read_unlock() invocation past the unlock operations to match
the non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but
that's harmless as the caller needs to hold RCU read lock across the lock
operation. The migrate_enable() call stays before the unlock operation
because there is no per CPU operation in the unlock path which would
require migration to be kept disabled.

Fixes: 0f383b6dc9 ("locking/spinlock: Provide RT variant")
Reported-by: syzbot+000c800a02097aaa10ed@syzkaller.appspotmail.com
Decoded-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/87jyrud75z.ffs@fw13
2026-06-21 11:51:13 +02:00
..
bpf mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
cgroup cgroup: Changes for v7.2 2026-06-17 12:03:56 +01:00
configs slab: support for compiler-assisted type-based slab cache partitioning 2026-05-14 10:44:09 +02:00
debug kgdb: update outdated references to kgdb_wait() 2026-04-21 16:41:54 +01:00
dma dma-mapping updates for Linux 7.2: 2026-06-17 12:20:21 -07:00
entry futex: Provide infrastructure to plug the non contended robust futex unlock race 2026-06-03 11:38:52 +02:00
events bpf-next-7.2 2026-06-17 09:18:14 +01:00
futex Locking updates for v7.2: 2026-06-15 14:21:14 +05:30
gcov Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
irq Locking updates for v7.2: 2026-06-15 14:21:14 +05:30
kcsan kcsan: test: Adjust "expect" allocation type for kmalloc_obj 2026-02-26 09:54:08 -08:00
livepatch Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
liveupdate kho: fix order calculation for kho_unpreserve_pages() 2026-05-26 11:01:49 +03:00
locking locking/rt: Fix the incorrect RCU protection in rt_spin_unlock() 2026-06-21 11:51:13 +02:00
module module: decompress: check return value of module_extend_max_pages() 2026-06-04 16:37:32 +00:00
power mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
printk printk: fix typos in comments 2026-06-02 15:36:06 +02:00
rcu Updates for the NOHZ subsystem: 2026-06-15 13:48:52 +05:30
sched sched_ext: Changes for v7.2 2026-06-17 12:10:11 +01:00
time A series of updates for the VDSO: 2026-06-15 13:57:13 +05:30
trace ring-buffer: Updates for v7.2: 2026-06-18 21:23:22 -07:00
unwind Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
.gitignore kheaders: rebuild kheaders_data.tar.xz when a file is modified within a minute 2025-06-24 20:30:37 +09:00
acct.c fs: move SB_I_USERNS_VISIBLE to FS_USERNS_MOUNT_RESTRICTED 2026-05-11 23:13:01 +02:00
async.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit_fsnotify.c audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
audit_tree.c audit: use 'unsigned int' instead of 'unsigned' 2026-05-26 17:15:30 -04:00
audit_watch.c audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
audit.c audit/stable-7.2 PR 20260615 2026-06-17 12:55:09 +01:00
audit.h audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
auditfilter.c audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
auditsc.c audit/stable-7.2 PR 20260615 2026-06-17 12:55:09 +01:00
backtracetest.c
bounds.c x86/asm: Remove ANNOTATE_DATA_SPECIAL usage 2025-12-03 16:53:19 +01:00
capability.c
cfi.c cfi: Move BPF CFI types and helpers to generic code 2025-07-31 18:23:53 -07:00
compat.c
configs.c
context_tracking.c context_tracking: Remove rcu_task_trace_heavyweight_{enter,exit}() 2026-01-01 16:39:46 +08:00
cpu_pm.c syscore: Pass context data to callbacks 2025-11-14 10:01:52 +01:00
cpu.c driver core: Replace dev->offline + ->offline_disabled with accessors 2026-04-26 23:51:02 +02:00
crash_core_test.c crash: add KUnit tests for crash_exclude_mem_range 2025-09-13 17:32:55 -07:00
crash_core.c kernel/crash: remove inclusion of crypto/sha1.h 2026-03-27 21:19:46 -07:00
crash_dump_dm_crypt.c crash_dump/dm-crypt: don't print in arch-specific code 2026-04-02 23:36:24 -07:00
crash_reserve.c kernel/crash: remove inclusion of crypto/sha1.h 2026-03-27 21:19:46 -07:00
cred.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
delayacct.c delayacct: fix uapi timespec64 definition 2026-02-08 00:13:32 -08:00
dma.c
elfcorehdr.c
exec_domain.c
exec_state.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
exit.c Scheduler updates for v7.2: 2026-06-15 14:50:18 +05:30
exit.h
extable.c
fail_function.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
fork.c mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
freezer.c freezer: Clarify that only cgroup1 freezer uses PM freezer 2025-10-30 20:10:27 +01:00
gen_kheaders.sh kheaders: make it possible to override TAR 2025-08-06 10:23:36 +09:00
groups.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
hung_task.c hung_task: explicitly report I/O wait state in log output 2026-03-27 21:19:40 -07:00
iomem.c
irq_work.c irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT 2026-05-11 16:28:04 +02:00
jump_label.c jump_label: use ATOMIC_INIT() for initialization of .enabled 2026-03-16 13:16:48 +01:00
kallsyms_internal.h kallsyms: Get rid of kallsyms relative base 2026-01-22 15:58:22 -07:00
kallsyms_selftest.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kallsyms_selftest.h
kallsyms.c mm.git review status for linus..mm-nonmm-stable 2026-02-12 12:13:01 -08:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.kexec liveupdate: kho: move to kernel/liveupdate 2025-11-27 14:24:33 -08:00
Kconfig.locks
Kconfig.preempt sched: Further restrict the preemption modes 2026-01-08 12:43:57 +01:00
kcov.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kexec_core.c kernel/kexec: remove inclusion of crypto/hash.h 2026-03-27 21:19:46 -07:00
kexec_elf.c
kexec_file.c kexec: derive purgatory entry from symbol 2026-01-31 16:16:07 -08:00
kexec_internal.h kexec: enable CMA based contiguous allocation 2025-08-02 12:01:38 -07:00
kexec.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kheaders.c
kprobes.c kprobes: Remove unneeded warnings from __arm_kprobe_ftrace() 2026-03-13 23:15:26 +09:00
kstack_erase.c sysctl: remove __user qualifier from stack_erasing_sysctl buffer argument 2025-11-27 15:44:53 +01:00
ksyms_common.c
ksysfs.c kernel: ksysfs: initialize kernel_kobj earlier 2026-04-03 19:39:52 +02:00
kthread.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
latencytop.c
Makefile exec: introduce struct task_exec_state 2026-05-26 11:02:01 +02:00
module_signature.c module: Give 'enum pkey_id_type' a more specific name 2026-03-24 21:42:37 +00:00
notifier.c
nscommon.c nsfs: tighten permission checks for ns iteration ioctls 2026-02-27 22:00:08 +01:00
nsproxy.c vfs-7.1-rc1.mount.v2 2026-04-14 19:59:25 -07:00
nstree.c nstree: tighten permission checks for listing 2026-02-27 22:00:11 +01:00
padata.c padata: Put CPU offline callback in ONLINE section to allow failure 2026-03-22 11:17:59 +09:00
panic.c bug/kunit: Core support for suppressing warning backtraces 2026-05-14 10:50:00 -06:00
params.c kernel: param: initialize module_kset in a pure_initcall 2026-06-08 23:27:56 +02:00
pid_namespace.c pid_namespace: allow opening pid_for_children before init was created 2026-03-20 14:44:26 +01:00
pid_sysctl.h
pid.c pidfd: refuse access to tasks that have started exiting harder 2026-05-19 08:57:47 +02:00
profile.c
ptrace.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
range.c
reboot.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
regset.c
relay.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
resource_kunit.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
resource.c PCI: Align head space better 2026-03-27 10:19:08 -05:00
rseq.c rseq: Reenable performance optimizations conditionally 2026-05-06 17:40:27 +02:00
scftorture.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
scs.c scs: fix a wrong parameter in __scs_magic 2025-11-12 10:00:13 -08:00
seccomp.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
signal.c signal: clear JOBCTL_PENDING_MASK for caller in zap_other_threads() 2026-05-22 15:19:31 +02:00
smp.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
smpboot.c sched/smp: Use the SMP version of idle_thread_set_boot_cpu() 2025-06-13 08:47:20 +02:00
smpboot.h
softirq.c softirq: Prepare for deferred hrtimer rearming 2026-02-27 16:40:13 +01:00
stacktrace.c
static_call_inline.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
static_call.c
stop_machine.c sched: Simplify ifdeffery around cpu_smt_mask 2026-05-19 12:17:37 +02:00
sys_ni.c rseq: Implement sys_rseq_slice_yield() 2026-01-22 11:11:17 +01:00
sys.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
sysctl-test.c
sysctl.c sysctl: fix uninitialized variable in proc_do_large_bitmap 2026-03-26 09:32:19 +01:00
task_work.c task_work: Fix NMI race condition 2025-10-29 10:29:54 +01:00
taskstats.c taskstats: set version in TGID exit notifications 2026-04-15 02:15:02 -07:00
torture.c torture: Add torture_sched_set_normal() for user-specified nice values 2026-05-24 09:38:47 +02:00
tracepoint.c tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() 2026-04-14 05:17:02 -04:00
tsacct.c tsacct: skip all kernel threads 2026-01-26 19:07:13 -08:00
ucount.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
uid16.c
uid16.h
umh.c umh: replace use of system_unbound_wq with system_dfl_wq 2026-05-07 11:30:08 -10:00
up.c
user_namespace.c Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
user-return-notifier.c
user.c ns: drop custom reference count initialization for initial namespaces 2025-11-11 10:01:32 +01:00
utsname_sysctl.c
utsname.c namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
vhost_task.c vhost_task_create: kill unnecessary .exit_signal initialization 2026-06-10 02:17:00 -04:00
vmcore_info.c mm.git review status for linus..mm-nonmm-stable 2026-04-16 20:11:56 -07:00
watch_queue.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
watchdog_buddy.c watchdog/hardlockup: improve buddy system detection timeliness 2026-03-27 21:19:47 -07:00
watchdog_perf.c watchdog/hardlockup: simplify perf event probe and remove per-cpu dependency 2026-02-08 00:13:35 -08:00
watchdog.c watchdog/hardlockup: improve buddy system detection timeliness 2026-03-27 21:19:47 -07:00
workqueue_internal.h workqueue: Show in-flight work item duration in stall diagnostics 2026-03-05 07:27:48 -10:00
workqueue.c workqueue: Changes for v7.2 2026-06-17 11:57:44 +01:00